| Autor: |
Curwin AJ; Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain.; Universitat Pompeu Fabra, Barcelona, Spain., Brouwers N; Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain.; Universitat Pompeu Fabra, Barcelona, Spain., Alonso Y Adell M; Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria., Teis D; Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria., Turacchio G; Institute of Protein Biochemistry, National Research Council of Italy, Naples, Italy., Parashuraman S; Institute of Protein Biochemistry, National Research Council of Italy, Naples, Italy., Ronchi P; Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany., Malhotra V; Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain.; Universitat Pompeu Fabra, Barcelona, Spain.; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain. |
| Abstrakt: |
The unconventional secretory pathway exports proteins that bypass the endoplasmic reticulum. In Saccharomyces cerevisiae, conditions that trigger Acb1 secretion via this pathway generate a Grh1 containing compartment composed of vesicles and tubules surrounded by a cup-shaped membrane and collectively called CUPS. Here we report a quantitative assay for Acb1 secretion that reveals requirements for ESCRT-I, -II, and -III but, surprisingly, without the involvement of the Vps4 AAA-ATPase. The major ESCRT-III subunit Snf7 localizes transiently to CUPS and this was accelerated in vps4Δ cells, correlating with increased Acb1 secretion. Microscopic analysis suggests that, instead of forming intraluminal vesicles with the help of Vps4, ESCRT-III/Snf7 promotes direct engulfment of preexisting Grh1 containing vesicles and tubules into a saccule to generate a mature Acb1 containing compartment. This novel multivesicular / multilamellar compartment, we suggest represents the stable secretory form of CUPS that is competent for the release of Acb1 to cells exterior. |
